Composite multilayer fabrics that form a barrier to passage of toxic chemicals have been developed for use in protective garments. Garments made of effective barrier materials provide safer working conditions by preventing hazardous materials from coming into contact with the worker's body. The need for protective garments has been emphasized in recent years by enactment of local, state, and federal laws and promulgation of regulations requiring their use under many circumstances.
A highly effective composite multilayer barrier fabric is disclosed in my prior U.S. Pat. No. 4,833,010, issued May 23, 1989. This fabric has a base sheet of a material such as nonwoven polypropylene that has internal void spaces, a sheet of a first multilayer film material laminated to one face of the base sheet, and a sheet of a second multilayer film laminated to the opposite face of the base sheet. The first multilayer sheet includes an inner film of ethylene vinyl alcohol with a film of nylon laminated to each face thereof and an outer film of heat sealable polyethylene. The second multilayer film has a middle film of polyvinylidene chloride with a film of ethylene vinyl acetate laminated to its inner face and a film of heat-sealable polyethylene laminated to its outer face. This composite fabric is highly effective against a wide spectrum of chemicals. In standardized tests using the ASTM F739 test method wherein the fabric is as exposed to the ASTM F1001 chemical test battery, which includes 15 chemicals representing numerous classes of compounds, no breakthrough for any of the chemicals in the test battery occurred during an eight-hour test period.
A problem which has been presented in preparing protective garments from the composite fabric described above is the difficulty encountered in forming leak-proof durable seams between pieces of the fabric. In order to provide an effective protective garment, the seams therein as well as the fabric must provide a barrier to passage of liquid or gaseous chemicals sought to be excluded. Conventional sealing tapes made up of material such as polyethylene are not fully effective when bonded to this fabric in that they fail to provide a desired barrier for many of the chemicals in the referenced test battery. In addition to forming an effective barrier, sealing tape for fabrication of garments should be readily heat-sealable and should be amenable to forming a strong and durable seam when applied to the fabric. Requirements also exist for seaming of other types of composite fabrics and for joining of such fabrics to components such as clear plastic visors and zippers in fabrication of protective garments.